1. Field of the Invention
The present invention relates to a color organic EL display using electroluminescence of an organic compound material and to a fabrication method thereof.
2. Description of the Related Art
In a conventional organic electroluminescence display apparatus using a color organic EL display, it is important to selectively form color light emission organic materials as color light emission devices in a fine pattern on a transparent electrode.
In providing such color emission devices on a transparent electrode a shadow mask method has been used in which, when a light emission organic material is selectively evaporated and formed as layer, an opening portion of a shadow mask is formed in a metal sheet (see FIG. 1). In FIG. 1, a transparent anode 102 is disposed below a transparent glass substrate 101. An organic fluorescent film and an organic positive hole transporting layer 103 are disposed below the anode 102. A metal cathode 106 that is selectively evaporated is disposed below the organic positive hole transporting layer 103. A metal sheet 104 as a shadow mask is disposed below the cathode 106 through a small space. An evaporation film 106A is disposed below the metal sheet 104. In addition, an evaporation material 105 is upwardly evaporated. Thus, the metal cathode 106 that is selectively evaporated and the evaporation film 106A that is layered on the metal sheet 104 as the shadow mask are represented as remaining portions. The anode 102 and the cathode 106 are selectively disposed in the shape of lines and columns. A scanning voltage for generating an image is applied to the anode 102 and the cathode 106.
However, in such a method, it is difficult to finely form a metal sheet corresponding to a fine light emission device area and accurately form an evaporation film to a light emission device area because of bend and expansion of a metal sheet. In addition, when the metal sheet contacts the positive hole transporting layer, the element portion breaks and thereby the light emission device becomes large and deteriorates accuracy. Thus, the resolution of the resultant display deteriorates. Moreover, since some light emitting devices do not light, the visual recognition characteristic lowers. Furthermore, the fabrication yield decreases. Thus, the conventional method is not sufficient for the visual recognition characteristic and fabrication yield. In other words, it is not suitable to use the shadow mask method of which an opening portion is formed in a metal sheet.
To solve such a problem, Japanese Patent Laid-Open Publication No. 2-176707 discloses a fabrication method for a color filter array device having a heated emboss surface. In the fabrication method, a plurality of dopant materials composed of sublimation coloring matters with different colors and respective acceptor devices composed of supporting members having coloring matter acceptor layers are used. The dopant materials are successively contacted with the acceptor devices. The dopant materials are contacted with heated emboss surfaces so that the dopant materials are heated in a pattern shape. Thus, the coloring matters are transferred to the acceptor layers. Consequently, an array of repetitive mosaic patterned coloring agents held on supporting members is fabricated.
However, since a metal sheet has a high heat conductivity, the heating roller heats the entire surface of the emboss surface of the sheet, sublimation materials, sublimate and transfer to other than the emboss surface. Thus, the dopant materials contaminate the acceptor elements. Consequently, color purity deteriorates.
In addition, since heat transfers in the state that the heating roller contacts the emboss metal, the contact surfaces should be highly accurate. Thus, the fabrication yield deteriorates. Moreover, since the heating temperature of the sublimation materials should be precisely controlled, the heating method using a heating roller causes the materials to unevenly sublimate.
Thus, when the related art reference disclosed in Japanese Patent Laid-Open Publication No. 2-176707 is applied to a color organic EL display, the colors of light emission devices fluctuate and some devices do not light.